Signals of Changing Climate from the Antarctic Terrestrial Environment

Peter Convey, British Antarctic Survey, Natural Environment Research Council
High Cross, Madingley Road, Cambridge CB3 0ET
UK tel + 44 1223 221588, fax + 44 1223 362616
E-mail p.convey@bas.ac.uk

Terrestrial ecosystems of the Antarctic Peninsula are structurally simple but well developed. This simplicity, in combination with contemporary rapid changes in several environmental variables, creates a natural laboratory probably unparalleled worldwide in which to unravel the biological consequences of climate change processes. The biota of these ecosystems are known to be limited by the twin environmental factors of low temperature and lack of liquid water. Superimposed on patterns of changes in these two variables is the recent modification of incident radiation, particularly changes in the timing of UV-B maxima, through the formation of the spring ozone hole. In principle, changes in all three physical variables may act singly or in combination, and lead to both positive and negative consequences for the biota. As well as experiencing changes at any specific location, the Antarctic Peninsula and islands of the Scotia Arc provide an environmental gradient from oceanic cool temperate to frigid continental desert conditions. Again ecosystem simplicity, combined with wide species and community distributions across this gradient combine to give a second natural model of climate change predictions, allowing analysis at scales between cell biochemistry and entire ecosystems.

Across this gradient, biological changes consistent with the predictions from climate amelioration are already visible. These largely take the form of rapid expansions in range and local population numbers amongst elements of the flora, particularly mosses and flowering plants. A range of field manipulation techniques have been used to demonstrate the potential for massive species and community responses to climate amelioration and demonstrate the importance of existing soil propagule banks, as well as to examine the biochemistry of response to changing radiation environments. Biochemical, physiological and ecological studies generally indicate that Antarctic species across the range of taxonomic groups represented possess considerable resistance/resilience and response flexibility to a range of environmental variables. The wide environmental variability inherent in the Antarctic terrestrial environment also means that predicted levels of change often fall well within the range already experienced. Thus, at least in the short to middle term, climate amelioration may well lead to positive responses from resident biota, at least while they remain partially protected through isolation from colonisation by more effective competitors. Organism and species responses are likely to be subtle and multifactorial in origin, arising from changes in resource allocation patterns and energy economics. However, the integration of these subtle responses may lead to much more visible impacts across communities and ecosystems.